Air quality in urban areas can be horrendous. For instance, in New York and Los Angeles the air quality is consistently below federal safety levels. So, how do you know how good/bad the air in your back yard is? Well, you could be living in a hotbed of pollution and not even know it, which is why this make-it-yourself air quality balloon should be your next DIY project. You just need a few tools, a couple of twenties and voila.

First of all, if you haven’t perused the Instructables site, you are missing out. Get over there right now — well, after you’re done with this article — and check out the amazing DIY projects they’ve got. It isn’t for the faint of heart, earlier this squelching summer they taught us how to make a DIY air conditioner so they’re not messing around. Now, they’re going to teach you all about the air quality in your own backyard. For around $40 you can make your very own backyard weather balloon/LED light/air quality sensor.

The pollution sensor seems pretty easy to make and is visually satisfying when you’re finished. The biggest investment of the whole thing is a $10 air quality sensor, and the rest of the parts seem to be the kind of things available at a local hardware store — the instructions come with a complete list and price tags so you know what you’re getting into. The LED lights that are placed inside the weather balloon turn green, orange/yellow or red depending on the air quality levels that the sensor is detecting. Green is good to go and red means watch out, get the community board on the phone and picket your local smoke stack.